Caddo madtom
| Caddo madtom | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Siluriformes |
| Family: | Ictaluridae |
| Genus: | Noturus |
| Species: | N. taylori |
| Binomial name | |
| Noturus taylori N. H. Douglas, 1972 | |
The Caddo madtom (Noturus taylori) is a species of fish in the Ictaluridae family. It is endemic to the United States. N. taylori was named in honor of William Ralph Taylor, U.S. National Museum, in recognition of his contributions to our knowledge of catfishes.[1] They average two to four inches in length, and weigh no more than a couple of ounces. N. taylori species have small to tiny or fragmented ranges, but are mostly found in the Caddo, Ouachita and Little Missouri rivers in southwestern Arkansas.[2] Ecological studies indicate that dam and bridge construction poses barriers to dispersal and migration of fishes in the Ouachita Highlands.[3] IUCNredlist.org states that better information is needed on life history, reproductive biology, and ecology of the Caddo madtom.[4] This species is listed as vulnerable on the IUCN Redlist. Limited range makes this species vulnerable to habitat destruction/degradation from impoundment, pollution, and other factors. Robison and Buchanan (1988) stated that "this rare species should be considered threatened due to loss of habitat".[5] Warren et al. (2000) categorized the species as "threatened" (likely to become endangered throughout all or a significant portion of its range).[6]
Geographic distribution
N. taylori was known only from the upper Caddo River, a tributary to the Ouachita River, Arkansas.[1] This small madtom is the second species (the other is Etheostoma palidodosum) apparently endemic to the upper water of the Caddo River, Ouachita River drainage,[7] which originates in the Ouachita Mountains of southwestern Arkansas.[1] They were found to appear in the upper Caddo River where the water is much clearer than the lower more turbid reaches below the impounded DeGray Reservoir, which is where their distribution seems to end. They have now been collected from other nearby rivers, the Ouachita and S. Fork Ouachita Rivers, connected to the same watershed.[3] The first known collection of this species was obtained from the Caddo River, near Glenwood, Pike County, on February 21st 1970. Since then, N. taylori has been collected from the Caddo River in Montgomery Co., Pike Co., and Clark Co., respectively, in southwestern Arkansas.[1] In principle, these fish are vulnerable to extinction by catastrophic watershed-scale environmental disturbance, and their distribution seems to have decreased in response to these vulnerabilities. This might be because species that specialize on headwater habitats might be particularly vulnerable to local extirpation because natural recolonization from adjacent rivers is unlikely.[3]
Ecology
The Caddo madtom is a specialist on headwater streams.[3] Food includes snails, isopods, ephemeropterans (mayflies), dragonflies, caddisflies, stoneflies, aquatic lepidopterans (aquatic moths and butterflies), aquatic beetles, and dipterans (true flies), but ephemeropterans and dipterans are the dominant items.[8] Habitat includes shallow, gravel-bottomed pools or shoals near shorelines of clear, small to medium upland rivers, especially well-compacted gravel areas below gravel riffles, where this madtom occurs under rocks, beneath large gravel, or among rubble.[5] It prefers well-compacted gravel areas below gravel riffles where it lives under rocks, beneath large gravel, and in the interstices of rubble.[8] Genetic results have implications for conservation and management of fish species like the Caddo madtom. At the within-drainage scale, fragmentation by natural or human activities (i.e., reservoirs) possibly affects individual movement and recolinization probabilities, resulting in genetic divergence (i.e., South Fork vs. Ouachita mainstem).[3] Causes for decline may include siltation and turbidity in farming areas, and the dewatering of habitats by hydropower operations. Another reason for decline that should be assessed is predators and competitors. Published articles on madtom predators and competitors were hard to find. Though, like all madtoms, they are known for their pectoral spines that contain saw-like teeth and a neurotoxin gland. These spines and toxins produce a painful sting when utilized, and indicate the presence of predators.
Life history
This is a species that truly does spend its “life in the rocks.” Spawning occurs from late April to May and it seems to occur only once during this time; however, no nests have been found to date.[8] Ova counts from ripe females range up to forty-eight mature eggs but average sixteen eggs per female.[5] Age of sexual maturity is yet to be discovered and determined and little is known about the Caddo madtom's reproduction. It is especially noteworthy in being the only madtom with heteromorphic sex chromosomes.[9] Much more information is needed on the life history of the Caddo madtom. A complete picture of their life history could give us much better insight into what actions are necessary to preserve this species’ longevity. More life history information could also impede or de-incentivize further biotic and abiotic human-induced changes that potentially reduce the abundance of these fish.
Current management
Ecological studies indicate that dam and bridge construction poses barriers to dispersal and migration of fishes in the Ouachita Highlands.[6] Construction is generally destructive to aquatic habitats of any kind, unless designed specifically to help species diversity, and even then it can cause harm. As stated before, Limited range makes this species vulnerable to habitat destruction/degradation from impoundment, pollution, and other factors. Robison and Buchanan (1988) stated that "this rare species should be considered threatened due to loss of habitat".[5] Warren et al. (2000) categorized the species as "threatened" (likely to become endangered throughout all or a significant portion of its range).[6] Noturus taylori appears to be vulnerable to local extirpation by small-scale disturbances; aquatic habitats in the region are impacted by local human activities (e.g., development, logging, gravel mining) that can adversely affect stream fishes.[3] Legislation is constantly being lobbied for the protection of all IUCN Redlist species. But, new avenues must be explored in order to find the answers needed to mitigate or even stop completely habitat degradation caused by human impact.
References
- 1 2 3 4 Douglas, Neil H. 1972. Noturus taylori, a New Species of Madtom (Pisces, Ictaluridae) from the Caddo River, Southwest Arkansas. Copeia 1972: Volume 1972, No. 4, pages 785-789.
- ↑ Burr, Brooks M., Eisenhour, David J., Grady, James M. 2005. Two New Species of Noturus (Siluriformes: Ictaluridae) from the Tennessee River Drainage: Description, Distribution, and Conservation Status. Copeia 2005: Volume 2005, No. 4, pages 783-802.
- 1 2 3 4 5 6 Turner, Thomas F., Robison, Henry W. 2006. Genetic Diversity of the Caddo Madtom, Noturus taylori, with Comments on Factors That Promote Genetic Divergence in Fishes Endemic to the Ouachita Highlands. The Southwestern Naturalist 2006: Volume 51, No 3, pages 338-345.
- ↑ NatureServe 2013. Noturus taylori. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.1. <www.iucnredlist.org>. Downloaded on 28 October 2013.
- 1 2 3 4 Robison, H. W., and Buchanan T. M. 1988. Fishes of Arkansas. University of Arkansas Press.
- 1 2 3 Warren, M. L., and M. G. Pardew. 1998. Road crossings as barriers to small stream fish movement. Transactions of the American Fisheries Society 127:637–644.
- ↑ Fruge, D. W. 1971. Fishes of the Caddo River, west central Arkansas. M.S., Northeast Louisiana Univ., Monroe, Louisiana.
- 1 2 3 Robison, H. W., and Allen, R. T. 1995. Only in Arkansas: A Study of the Endemic Plants and Animals of the State. University of Arkansas Press.
- ↑ LeGrande, William H. 1981. Chromosomal Evolution in North American Catfishes (Siluriformes: Ictaluridae) with Particular Emphasis on the Madtoms, Noturus. Copeia 1981: Volume 1981, No. 1, pages 33-52.